The anterior surface of the eye functions as a barrier to the external environment and protects the delicate underlying structures from injury. This protection is provided through the elaboration of the corneal, limbal and conjunctival epithelia. As self-renewing tissues, these epithelia are governed by stem cells, which play a crucial role in tissue homeostasis, regeneration, tissue transplantation, gene therapy, and in the pathogenesis of several anterior surface epithelial diseases. My work during the past decade has contributed to the identification of stem cells within the corneal and conjunctival epithelia. My recent findings suggest that the meibomian gland may be the site of the ultimate conjunctival epithelial stem cells, and thus may play a role in maintaining the conjunctival epithelium. The long-term goal of this project is to understand the biological properties of corneal and conjunctival epithelial stem cells. Towards this end we will: (i) determine the role of the meibomian gland in the homeostasis of the conjunctival epithelium. (ii) continue to identify and characterize genes that may govern the limbal stem cell population. Data obtained from these studies, should help us to understand the role of stem cells in controlling growth and differentiation of the corneal and conjunctival epithelia. These studies should form the foundation for a better understanding of the etiology of certain problems associated with limbal stem cell deficiency (e.g. persistent corneal epithelial breakdown), as well as neoplastic transformations giving rise to the unusually aggressive mucoepidermoid and sebaceous carcinomas.